In some resource-constrained systems, sleep states are used to conserve power. For example, wireless sensor networks (WSN) are one type of resource-constrained system that benefits from the use of low-power sleep states. During a sleep state, normal operation of a system (or parts of the system) is halted to conserve energy. The system may be signaled to exit the sleep state by a wakeup event detector circuit, for example, so that certain events can be observed and/or processed. One tradeoff faced during design of sensor network systems is maximizing an amount of time spent in sleep states to conserve power while minimizing any data loss associated with certain important events (including those leading up to and/or including a wakeup event). In systems that rely upon a wakeup circuit to detect certain events during a sleep state, data that should have been captured before, during, or shortly after a wakeup event may be lost.